This application is based on Japanese Patent Applications 2000-107141 filed on Apr. 7, 2000 and 2000-305316 filed on Oct. 4, 2000, all the content of these applications is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an effluent treating technology to decompose and to remove chlorine-based organic matter contained in effluent, and in particular, to an effluent treating technology capable of treating effluent with high efficiency and suppressing discharge of secondary products such as chlorine-based gas.
2. Description of the Related Art
Chlorine-based organic solvents have high cleaning capability, high stability, and incombustibility and have been therefore well known as good cleaning agents.
According to the Atmospheric Contamination Prevention Law, chlorine-based organic matter has been recently designated as priority substance, voluntary control substance, and designated substance among the hazardous air contaminating substance. Quantity of chlorine-based organic matter contained in effluent and exhaust gas from a cleaning apparatus of a dry-cleaning system and the like must be decreased not to exceed limit values as the effluent standards. For this purpose, an adsorbing method using activated carbon, a thermal vaporizing method, and the like have been heretofore employed.
In the adsorbing method using activated carbon, since the activated carbon loses the adsorbing function at its saturated stage of adsorbtion, the activated carbon must be replaced at this stage. However, it is difficult to detect a point in time when the activated carbon loses the adsorbing function. Additionally, it is necessary to entrust treatment of the saturated activated carbon as a designated substance to a specialized plant or company or it is neccessary to desorb the saturated activated carbon by steam or the like before the activated carbon is used again. However, these procedures have low efficiency and require additional cost.
When the thermal vaporizing method is used, concentration of chlorine-based matter in the effluent can be lowered down to a standard value designated by the law or less by vaporizing the chlorine-based matter.
In the method, however, when the chlorine-based matter has a low concentration in the effluent, the treatment cannot be fully effectively conducted and hence treatment efficiency is lowered. Vaporized chlorine-based organic matter not decomposed is discharged into air. Therefore, quantity of chlorine-based organic matter contained in the discharge gas cannot be lowered to the limit as the effluent standard in some cases.
Recently, there has been proposed, for example, in JP-A-8-323346 an effluent treating technology employing a photocatalytic material which is activated at an ultraviolet-ray level of natural sun light or fluorescent light and which thereby decomposes chlorine-based organic solvent and the like to render the solvent harmless.
The technology however is attended with a problem that no consideration has been given to a point to render harmless the chlorine-based gas produced as a result of decomposition of chlorine-based organic matter.
Since the regulation of exhaust of chlorine-based organic matter is getting severer these days, an effluent treating technology having high decomposing efficiency has been needed.
It is therefore an object of the present invention to provide an effluent treating technology to decompose and to remove chlorine-based organic matter contained in effluent in which the treatment is conducted with high efficiency to resultantly suppress discharge of secondary products such as chlorine-based gas.
In accordance with one aspect of the present invention, there is provided an effluent treating method comprising the steps of; vaporizing effluent containing chlorine-based organic matter and producing vaporized gas containing chlorine-based organic gas; reacting said vaporized gas with photocatalytic material, with irradiating ultraviolet light, and decomposing the vaporized gas; and absorbing, adsorbing, or neutralizing said reacting step.
In accordance with one aspect of the present invention, there is provided an effluent treating apparatus comprising an effluent vaporizing tank; a photocatalytic material put in a container; an ultraviolet ray source irradiating ultraviolet light onto the photocatalytic material; a treating tank filled with an absorbing, adsorbing, or neutralizing agent; a first path connecting the effluent vaporizing tank and the container; and a second path connecting the container and the treating tank.
In the effluent treating apparatus according to the present invention, high photo oxidization efficiency and high aeration efficiency minimize the period of time required for the effluent treatment and lower the total cost. Quantity of chlorine-based organic matter contained in the effluent and/or discharge gas and quantity of chlorine-based gas as a secondary product can be reduced respectively to discharge standard values designated by laws. This contributes to suppression of environmental contamination.
Since the vaporizing section may be constituted with an apparatus or a device used in the prior art, any new technology is not required in this point and hence the total cost can be lowered.
The sections and members to be brought into contact with chlorine-based gas highly corrosive against metals are fabricated using corrosion-resisting materials. The granules of photocatalyst (photocatalytic granules) can be cleaned in this system. The configuration can be used for a long period of time and hence the cost for maintenance thereof is minimized.
Since the overall system configuration is elongated in a perpendicular direction, the system can be installed in a place with a small area in a horizontal plane. The system includes casters on its bottom section and can be therefore easily moved from one position to another position.
The system can be easily connected to various kinds of cleaning apparatuses which discharge waste fluid containing chlorine-based organic matter.
In the effluent treating method of the present invention, the time and the cost required for the treatment of effluent can be reduced, and quantity of chlorine-based organic matter contained in effluent and/or discharge gas and quantity of chlorine-based gas as a secondary product can be reduced to the respective discharge standard values designated by the pertinent laws.